1. Technical Field
The present invention relates to a color sensor, and more particularly a color sensor wherein the construction of the sensor is simple, and wherein the sensor is easily integrated and large-scaled.
2. Background Art
Hitherto, color sensors have been used in order to obtain information about the spectra of incident light.
Among color sensors, color sensors using multi-junction semiconductors are considered to be favorable since they can detect each spectrum of the incident light without distribution thereof by color filtering and the like. A color sensor like this generally has a construction as shown in FIG. 3. FIG. 3 shows a two-stage pin junction as an example. In FIG. 3, numeral 11 is a transparent electrode such as TCO, numeral 12 is the first stage pin junction. A transparent conductive film 14 is provided between the first stage pin junction 12 and the second pin junction 13. Numeral 15 is a back electrode provided on the side opposite to the incident light.
In an element shown in FIG. 3, the short wave light (blue light) has weak penetration ability, so that it results mainly in photoelectric current from the first stage pin junction, and the long wave light (red light) induces a photoelectric current in the first and the second stage pin junctions. If the thickness of the first stage pin junction is made thin enough, the red spectrum can be detected by detecting the photoelectric current from the second stage.
However, it is necessary in conventional oolor sensors comprising multi-junction semiconductors that three terminals are provided, and that a transparent conductive film is provided between both pin junctions. Therefore, if the number of stages is increased to three stages and four stages, it becomes necessary that four terminals and five terminals are provided respectively, and that two layers and three layers of transparent conductive films are provided respectively. Accordingly, conventional color sensors have drawbacks in that the construction thereof becomes complex when an integrated color sensor is made or when they are used as linear sensors. Complication of construction, as a matter of course, brings about complication in the manufacturing process and a commensurate increase of cost. Also, there is a problem that the yield of the color sensors decreases because of a short circuit being formed in a pin junction even if there are a few pin holes therein, since the electric potential of the transparent films provided between each pair of pin junctions is considered to be almost equal.
Taking into consideration the above-mentioned drawbacks, it is an object of the present invention to provide a color sensor wherein the construction of the sensor is simple, and it is easily integrated and large-scaled.